Ice eliminating system



Aug. 9, 1949.

p. M. LAWRENCE ICE ELIMINATING SYSTEM 4 Sheets-Sheet l Filed Jan. 30,1942 INVENTOR. DONAL D M. LA WRENCE BY I A TTORNEY.

s- 9, 1949. D. M. LAWRENCE 2,478,492

' ICE ELIMINA'I'ING SYSTEM Filed Jan. 30, 1942 4 Sheets-Sheet 2INVENTOR. DONALD M. LA WRENCE WKW/ A TTORNE Y1 Au 9, 1949. D. M.LAWRENCE 2,418,492

ICE ELIMINATING SYSTEM Filed Jan. 30, 1942 4 Sheets-Sheet 3 g INVENTOR.

DONALD MLAWRENCE ATTORNEY Aug. -9, 1949.

4 Sheets-Sheet 4 INVENTOR. DONALDMLAWRENCE Patented Aug. 9, 1949 ICEELIMINATING SYSTEM Donald M. Lawrence, Caldwell, N. J., assignor toBendix Aviation Corporation, South Bend, 1nd,, a corporation of Delaware'Application January 30, 1942, Serial No. 428,948

11 Claims.

This invention relates to ice eliminating systems, and particularly to asystem for removing ice from the leading edges of aircraft surfaces.

Prior to the present invention, it has been common to utilize rubbertubes or boot elements along the leading edges of aircraft wings andtail surfaces in order to break up accumulations of ice on thesesurfaces and permit the ice to be carried away by the air stream.

In the patent to Gregg, 1,990,866, there is described an ice eliminatingsystem wherein rubber boots are inflated in accordance with a definitecycle of operation, the air from one inflated boot being directed by adistributing valve into a second inflatable boot, until the pressure inthe two boots is equalized. Upon equalization of air pressure in theboots, additional air from a pressure pump is directed into the secondboot to complete the inflation. The present invention is an improvementover the system described in the Gregg patent, and is directed to anovel air distributing means and method whereby the elimination of icemay be expedited.

In the present invention the distributor valve is so arranged as toflrst'port air under pressure to the selected boot for a firstpredetermined time interval, then to close on the air pressure and for asecond predetermined time interval, controlled by the speed of the motorand by the size of the port opening, to port the air under pressure inthe boot to the atmosphere, thereby allowing a portion of the air toflow out of the inflated boot. The valve then closes the port to theatmosphere, and opens a port connected to a source of suction for athird predetermined time interval. This then evacuates the boot andholds it to the airfoil contour. The action of first dumping some oftheair from the boot overboard to atmosphere thereby reduces thequantity of air to be forcibly evacuated from the boot through thesuction or vent line.

It is an object of the present invention to provide an ice eliminatingsystem for aircraft employing inflatable boot members, wherein the bootis first inflated, then deflated, and finally, placed under suction inseparate steps for predetermined time intervals.

. It is a further object of the invention to provide a-system wherein aboot member is subjected to the cycle of inflation to a superatmosphericpressure, deflation to atmospheric pressure, and connection to a sourceof sub-atmospheric pressure in separate phases.

Yet another object of the invention is the pro- 2 vision of a noveldistributing member for carrying out the above novel system.

According to the invention, there is provided a distributor particularlydesigned for usewith inflatable boots for the elimination of ice fromaircraft and adapted when actuated to connect each chamber of aplurality of boot chambers controlled thereby cyclically to a source offluid pressure, to atmosphere, and to a source of suction, wherein whenthe pressure source is out OE and the distributor arrested all of theboots are connected to the suction source. The improved distributor maybe operative to connect each chamber of a plurality of chambers oneafter the other to a source of fluid pressure or the atmosphere and allof the chambers simultaneously to a source of suction whereby, when thesource of pressure is eliminated, all of the chambers will be evacuated.

Other objects will appear from a study .of the following specificationwhen made in conjunction with the attached drawings, throughout whichlike numerals designate like parts.

Fig." 1 is a schematic showing in plan of One installation of the systemof the present inven-- tion.

Fig. 2 is a view, partly in elevation and partly in section, of thenovel distributing valve of the present invention.

Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. 2.

Fig. 4 is an end elevational view of the distributing valve of thepresent invention.

Fig. 5 is a perspective of the valve element which is incorporated intothe distributor valve assembly of the present invention;

Fig. 5A is an end elevational view of the valve element shown in Fig. 5;and

Figs. 6 and '7 are sectional views of the distributing valve in twodifferent positions in its cycle of operation.

In general, the invention includes the method, and the means forcarrying out the method, wherein a boot element is first inflated withair from a pressure source, then deflated to atmospheric pressure, andthereafter, opened to a source of suction for maintaining thebootinteriors at low pressure toprevent boot vibration or boot expansionat low atmospheric pressures.

As shown in Fig. 1, I0 is an aircraft, shown in .phantom, having wingmembers II and I2, motors 3 plurality of groups of such tubular members,designated I6, I1, I8, I9, 20, 2i, and wing 12 contains correspondinggroups Hi to 2!. Each of these groups extends for a definite portion ofthe wing span. For example, the tubular members in groups [6 and I6extend to the wing tip, groups 2| and 2| extend inwardly to thefuselage, and each of the other (groups extends outwardly to the nextadjacent group. The additional groups 22 and 22 of tubular membersextend along the leading edge of each side of the horizontal stabilizerof the tail portion l5, and another group 23 extends along the leadingedge of the vertical stabilizer or rudder post of the tail portion IS.The different wing groups of in flatable members have connection toparticular ports of air distributors 24 and -'25-*through air ducts 26,and the different groups of inflatable members on the tail portion haveconnection to particular ports of an air distributing valve 21 throughthe air .duetst-Zil. 'si-n'ceiit is impossible to show the iceeliminating system :in true scaled relation to the aircraft 0, thedifierent groups or inflatable members which extend along the leadingedge f the wings :and the tail surfaces are -.:s'hown as distributedrather largely over the smrface of the Y'Ciiiift, :and the air :ducts.are :repretented-schematically afterthe fashion of anrelectnical*wiring di-a grain.

Engine I:3=id1fives a pressure pump :29'a'nd a suction hump E30, :andengine :14 drives a pressure iprnmp 31 anda suction pump 32. Pumps :29and 34 :are .'connected through their respective conomits 33 and. :34-to a junction :member '35, from which a single pressurefdistributingwline '36 extends arearwardly of the Junction vmember '35.Pumps and' 32 rare 'jo'ined tosanother portion or junction member 135through their respective conduits 31 and 38, and a single suction line:39 extends rearward'ly from 'a T ="conne'ctio'n taken .i rom theiroined isuction fconduits 3 and '38. The main pressure line 36 has 'a-"c'onne'ct-ion, which will be better understood :firom :a later-description of the air distributing waives, 'tozthe distributing valves24 Band sand also a similar connection to the distributin valve 21.Suction line 39 has "connections thefdistributing'valves 25 "and 2;! sin.a manner will also be Eanpa'rerrt :from the later description of thedistributor valves.

Earthen, =a ."ch'eckvalve14'0, through which "air :may

be drawn to a low pressure point exteriorly of the plane-:open'stosuction lineal-9.

Particular reference to FEigs. 3 :and '4 should he had for ::adescription of the air distributing waives 124., 2 5 and :21. *Sincethese units are 'basically similar, the'tdescriptionwill he confined toon'e, valve -24. :electric motor -'4'-l which may be driven by the craftpower "supply that may be connected to the motor :at the terminal post*42, Ri'ontr'ols the rotation iof a shaft '43 extending within thehousing 44 of the distributing valve, ihous'ing c'on tarns speedreduction units, such as a plurality :of worm :and gear drives 45,i'ot'ate the transverse shaft 46=at a suitab'ly slow s eed for theproper distribution of air 'to the inflatable boot members. A igenerallycylindficeil rotatabl'e vane 41, which is cl'early shown in perspectiveFig. 5, is oontaine'd "within each of the =distributiirg heads 48 "and49, and is driven by the tramsverse, double-ended shaft -46, keyed tothe last gear or the speed lredu'ction unit 45.

Distributing heads 48 and 49 are identical, and each includes acyliridric'al body portion =5 I, from which live obliquely extending,radial ports or *boot connections 52 pr'oiec't. Each-of these bootconnections is open to a particular rubber boot or series of bootsthrough conventional air tubing, not shown in Fig. 2, but indicatedschematically as one of the tubes 26 or 28 in Fig. 1. Body portion 5i isfitted with an interior metal liner 53, against which the outer surfaceof the cylindrical valve 47 is rotated by motor 4|. This liner 53, asWell as the body portion 52] {has a lport openin 54 placed under each ofthe boot "connections 52. Liner 53 also has a single suction connection55, which opens into a manifold space 56 extending throughout thecircumference of body portion 5|. A series of port openings 51, equallyspaced about the circumference of liner 53, falls within themarrifoldspace 56 in line axially with the series 'of port openings 54.

Each of the distributing heads 48 and 49 carries an axially extendingatmospheric air port connection 58, and this connection 58, along withbody portion 5|, is secured to a central housing and standard 59, bymeans of :a series of studbolts 61i.-

check valve 611 is shown closing a'ir exhaust port 62, and a springmember 63 urges valves 6| closed, although, as will be later shown,airunder certain conditions will cause valve 6! to be swung "about itspivot '54 to open position. The central housing portion '59 contains anair inlet 65, which opens :i-nto distributing heads 48 and 14,59 throughcircular apertures 66.. V

Considering Fig. 5 along with Fig. '2, it will be seen that valve member4'! has an end port 61 opening "axially :of valve 4-1, through whichfairunder pressure from a pressure :pump may flow from air 'iri'le't '65 tobe distributed in the manner that will be described :later. Asecondaxial opening 68 is iormed in the outer wall 69 "of valve 41. 'Gpen'in-g*268 forms an air exhaust passagewa :for the dumping of air {overboardto atmosphere through check valve 61' and port connection 58. Three moreports, all opening radially, are contamed in valve 4-1. The largest ofthese. port openings it, extends axially a sufficient length toestablish alt-flow between any two aligned ports 54 and 51 in the liner53. The next largest 7 port opening M, is axially coextensive with theport openings 54 in liner 53. The last radial opening in valve "41,namely, port opening '12, extends a ally for'thesame d'istance as portopening H,

is 'of considerably less "extent circumferentia lly', as will be pointed-out later. The circumrl erential extent-of each of apertures 10," andI2 bears "a definite relation to each other and to the c'ycleofoperatiomwhich consists of the inflation of about, the dumpingof airfrom'the boot to the atmosphere, and the opening of the boot to thesuction pump, which cycle is carried out in one revolution of valve 4for each of the five boot ports '52.

"Thecycle 'can'be readily understood after considering the rotation ofthe valve and the distri- '-'bution-ofai'r with respect to one of theboot connections 52, for example, the top boot connection shown insection in Fig-'2. Considering'valve '4 to :be rotated clockwise, asshown in Fig. 5, fpfort opening ll Wi-ll'pass under the top bootconection 5-2 at a fixed speed, depending upon the initial speed. ofmotor 41 and the train value of the reduction gearing 45. While portopening H is in communicationwith this boot connection 52, air is beingadmitted under pressure to the boot "connected thereto from the pressureline 36 through the air inlet in connection therewith, and through theports 56 and 61. As port opening H is rotated past the top bootconnection 52, the cylindrical 'sui faceof valve 41 will seal con- 'thedistributor line 36. driven valves 24, 25 and 21 are not in operationwhich aperture '1 5. nection '52," maintaining the boot inflated untilport' opening 12 comes under boot connection 52. For an intervaldetermined by the speed of the valve 41 and the angular size of portopening 12, the air under pressure from the boot will be opened to theatmosphere through port 68, check valve 6| and atmospheric airconnection 58. The boot pressure will'there'iore drop until it equalsthe atmospheric pressure, at which point check valve will close andprevent atmospheric air from entering the boot connection 52. Portopening 12 will have then passed completely out of communication withtop boot connection 52, and this connection will be placed incommunication with the suction connection 55, which, of

course, is in circuit with suction line 39. During tion of distributorvalve '41. r A normal speed of operation may be one revolution of valve41 in forty seconds, and the port openings 10, H and 12 will be adjustedin size to fit a particular installation of boot elements. It isintended that all boot elements not being inflated through port openingII, or dumped to atmosphere throughport opening 12 and port 68, shall beplaced under suction through port and suction connection 55, andtherefore, port 10 should be large enough in circumferential extent toplace three boots under suction at any one time.

* When the motor-driven-valves 24, 25 and 21 are'not in operation, allthe boot connections are placed under suction. In the arrangementshownin Figure 1 the junction member 35 has connected thereto the pressureconduits 33 and 34 and suction conduits 31 and 38. The junction member35 includes a suitable gate or control valve for alternately connectingthe pressure lines 33 and 34 or the suction lines 31 and 38 to Thus whenthe motor the valve 35 may be shifted so' as to close or disconnect'thepressure lines 33 and 34 from the distributor line 36 and open orconnect the suction lines 3'! and 38 to the distributor line 36. Thecontrol valve may be adjusted manually or may be positioned by suitablepower means.

, sure, will cause the pressurein line 39 to be maintained at asulficiently low value to keep the boot elements tightly against theskin of the craft,

thus eliminating the flutter and vibration of boots employed in theconventional system, such as that shown in the Gregg patent aboveidentified. So that the particular boot connection under falls when thesystem is stopped may be placed under suction, the small slots 13 areprovided so that in the "off position,-there may be a continuous suckingof air from the boot connection 52, under which port opening ll stops.In order that the boot connection under which port opening 12 stops mayalso be open to suction, a small-hole 14, as shown in Fig. 2, is drilledin the wall between port openings H and I2. Slots l3 and opening 14 areso small that during operation of the ice eliminating system, they donot offer substantial interference with the inflating of the differentboot members 52, and thus, each of the port openings 10, H and 12 iseffectively isolated or chambered from the other two.

The foregoing may also be accomplished by arranging the rotary valve 41,as shown in Figure 6, so that at the opening 12 the rotary valve 41 isspaced slightly from the liner 53 and thereby provides a restrictedpassage between the rotary valve 41 and the liner 53 extending from theopening 51 to the openings 52 and 12. Thus after the super atmosphericpressure has been exhausted from the connected boot through the valveopening 58 and valve -6l has closed the same, suction may be applied tothe boot through the latter restricted passage between the rotary valve41 and liner 53.

It will be seen, moreover, that if the valve 41 be stopped in the latterposition and the super atmospheric pressure be terminated through line35 without the connection of the suction lines 31 and 38 thereto, thensuction may be applied through the restricted passage 14 to port H andslots [3 and the boot connected thereto, as well as to the bootsconnected to openings 10 and 12.

Thus all of the boot connections may be effectively placed undersuction, when the system is not in normal operation.

While only one embodiment of the present invention has been shown in thedrawing, it is to be understood that various changes may be made withoutdeparting from the scope of the present invention. For this reason, itis intended not to limit the invention by the description herein givenas an example, but solely by the scope of the appended claims.

/Vhat is claimed is:

1.' An air distributing device comprising a housing, a cylindrical valvechamber, a rotatable valve therein, said valve having a cylindricalsurface, means for rotating said valve, an axially disposed air inletport to said valve, a plurality of radially disposed boot ports formedin said housing, a plurality of suction ports equal in number to saidboot ports and axially aligned therewith, said suction ports openinginto a manifold, a suction outlet in communication with said manifold,an axially disposed air exhaust port formed in said housing, a checkvalve disposed over said air exhuast port and biased. to preventre-entry of exhausted air, a first valve aperture formed in thecylindrical surface of said valve in registry with each of said bootports in succession, said first valve aperture being in communicationwith said air inlet port, a pair of valve apertures, one formed in saidcylindrical surface for successive registry with each of said boot portsand the other formed axially for communication with said air exhaustport, a dividing wall formed in said valve for isolating said firstvalve aperture from said pair of valve apertures, an additional valveaperture in said cylindrical surface, said additional aperture disposedfor simultaneous registry with one of said boot ports and one of saidsuction ports, and means formed in said valve for isolating saidadditional valve aperture from said air inlet port, from said firstvalve aperture, and from said pair of apertures.

2. An air distributing device for use with inflatable bootsfor theelimination of icefro-m an 7 aircraft, rcomprising anchousing mailingaevalve -chamber, a'valve; rotatable therein; said, valvebe- Ling."dividedginto ,three 1 separate compartments,

port, the secondof sai=dcompartments provid;'

: ing separate communication between one of said boot ports and saidair..exhaust port, the third ofesaid compartments providing separatecommunication-between one ,of said boot ports and :saidsuction port:means, and means for rotating said valve toiprovide a predeterminedsequence of V aconnections between the boot ports and the other :ports.

J3.,An air distributing device-for use withan inflatable boot: forthebelimination of:ice from ranzaircraft, comprising a housing, acylindrical valve chamber therein, a cylindrical rotatable valve in saidchamber, a'portflo-r connection to said boot, an air inlet port,;an airexhaust port, .andsuction port means in said housing, all opening intosaid valve chamber, said air inlet and said air exhaust :p-ortsibeinglocated at opposite ends of said chamber, axially thereof, said valvehaving one compartment containing apertures registrable with said bootport and. 5&id'fll! in- -inlet ,portga secondcompartment havingapertures registrable Withsaidboot and said air exhaust port, a thirdcompartment having an aper- -tureregistrable With said boot port andsaid suction:portmeansand means for rotating said valve to provideapredetermined sequence of con- ..nections between the boot port and theother ports through said apertures.

4., Ari-air distributing device comprising a housing, .a-cyhndricalvalve chamber, a rotatable valve therein, said valve beinggenerally-hollow with a cylindrical valve surface, apluraliw of radiallydisposed air distributor portsopening into said chamber, suction 'port,means, .air inlet port 'means and air, exhaust port means opening into"said chamber, a check. valve disposed over said air exhaust port meansand biased to prevent re-entry of exhausted air, a vfirst pair ofapertures formed in said valve, registrable, .respectively, with one ofsaid air distributor ports and;

said air inlet port, a'second pair of apertures formed in said valve andregistrable, respectively, with one of said air distributor portsandsaid air exhaust port means, an additional aperture formed in saidvalve and registrable, respectively,

with one of saidair distributor potrs and said suction port means, andpartition means formed in said valve for isolating said additionalaperture from each ofv said pairs of aperturesand said pairs ofapertures from each other, and means for continuously rotating saidvalve so as to effect a predetermined sequence of connections betweenthe air distributor ports and said suction port means, air inlet portmeans and air exhaust port means.

5. A fluidimedium distributing device for use with inflatable iceeliminating members ior-air- V a craft, comprising a casing,connections'provided on said casing for each of the inflatable members,

a pressure fluid inlet; connection, an atmosphere connection, and asuction connection, a distributor element in the casing, means to rotatethe distributor element-said distributor element -operative when rotatedtoconnect-each inflatable member cyclically with ...the pressure fluid,,the

iiatmosphere and-thesuction connections, and said rdistributor elementincluding means wherebyupr, on the pressure fluid connection beinginterrupted and'rotation Of the distributor elementbeing ar- 5 rested.the distributor may connect all of the inflatable membersto a source ofsuction.

6.,A fluid medium distributing device for use with-inflatableiceeliminatingmembers for aircraft, comprising a casing, connectionsprovided 10 ion saidcasing for each of the inflatable members, apressure fluid inlet connection, an atmos- :phere:connection, a suctionconnection, a distributor element, means to rotate the distributorelement, thedistributor element including 1151a first compartmentadapted to register successively each inflatable member connection withthe pressure .fluidconnection, a second compart- 'ment=adapted toregister successively eachinflatable member connection with theatmosphere ,connection, and ,a third compartment adaptedto registersuccessively each inflatable member, connection with the suctionconnection, said distributor element also including means :whereby uponthe pressure fluid connection being interrupted and 1 rotation of thedistributor .ele-

ment being arrested the distributor may connect alliof the inflatatblemembers to a source of suction.

'7. A system for the removal of ice from airfoil 3o surfaces ofaircraft, comprising, an inflatable ',boot,;flrst means providing asource of a fluid medium under super atmospheric pressure, second meansprovidinga source of. suction, means operable selectivelytoconnect saidboot. to, said source ofsuper atmospheric fluid pressureto inflate saidboot and to connect said boot .to .atmosphere tordeflate said boot,check valve means to control the atmosphere connection so asto permitgfluid medium under super atmospheric 40 pressure to exhaust from the,boot, but precluding ;re-entry of .said fluid medium from theatmosphere, and restricted fluid conduit means abeqtweenrsaidiboot andsaid source of suctiomfor deflating said boot under suction upon saidsuper .45 atmospheric fluid pressure being exhausted from;said:;boot:through' said atmosphere connection. .8,.,,.A fluid. mediumdistributing device comprising,ia casing, aplurality of fluiddistributor-connections provided. on said casing, a pressure fluid:inlet connection to the casing, an' atmosphere :iconnection to thecasing, a suction connection, a distributor element in the casing, meansto rotate the: distributor element,- the distributor element including afirst compartment adapted to register isuccessively each fluiddistributor connection with the pressure fluid connection, a secondcompartment adapted toiregister successively each of'the fluiddistributor connections with the at- -mosphere connection, and a thirdcompartment, a manifold for said casing and havingsuction ports equal innumber to and axially aligned with the fluid distributor connections,said suction w-connectionopening into said manifold, 'said third.--compartment 'adapted to successively register Withth-e axiallyaligned suction ports and fluid distributor connections, and meansincluding a =restricted,passage connecting said first andsecondcompartments, whereby upon the pressure Ufluid connectionbeinginterrupted. and rotation iof" the distributor element being arrestedthe distributor element may connect all of'the fluid dis- 'tributorconnections to a source of suction.

9. Afluid medium distributing device, comprisring, a casing, aplurality, of fluid distributor con- 7filinectionsrp fovided onsaidcasing, a pressure, fluid inlet connection to the casing, an atmosphereconnection to the casing, and a suction connection, a distributorelement in the casing, means to rotate the distributor element, thedistributor element including a first compartment adapted to registersuccessively each fluid distributor connection with the pressure fluidconnection, a second compartment adapted to register successively eachof the fluid distributor connections with the atmosphere connection, anda third compartment, a manifold for said casing and having suction portsequal in number to and axially aligned with the fluid distributorconnections, said suction connection opening into said manifold, saidthird compartment adapted to successively register with the axiallyaligned suction ports and fluid distributor connections, and meansincluding a restricted passage connecting said first and secondcompartments, whereby upon the pressure fluid connection beinginterrupted and rotation of the distributor element being arrested thedistributor element may connect all of the fluid distributor connectionsto a source of suction, and a check valve in the atmosphere connectionfor permitting fluid under super atmospheric pressure and returningthrough one of said fluid distributor connections to exhaust whilepreventing passage of fluid medium through the atmosphere connection tosaid fluid distributor connection.

10. A fluid medium distributing device, comprising, a casing, aplurality of fluid distributor connections provided on said casing, apressure fluid inlet connection to the casing, an atmosphere connectionto the casing, and a suction connection, a distributor element in thecasing, means to rotate the distributor element, the distributor elementincluding a first compartment adapted to register successively eachfluid distributor connection with the pressure fluid connection, asecond compartment adapted to register successively each of the fluiddistributor connections with the atmosphere connection, and a thirdcompartment, a manifold provided in said casing, said suction connectionopening into said manifold, and said manifold provided with suctionports equal in number to and axially aligned with the fluid distributorconnections, said third compartment adapted to successively registerwith the axially aligned suction ports and fluid distributor connection,and means including a restricted communication provided between saidfirst and second compartments, whereby when the source of fluid pressureis cut off and the distributor element is stationary the distributorelement may connect all of the fluid distributor connections to a sourceof suction regardless of the position in which the distributor elementcomes to rest in its casing.

11. For use with an inflatable element for the removal of ice fromairfoil surfaces of an aircraft; a control apparatus comprising, incombination, a unitary housing having an intake port for connection to asource of super atmospheric pressure, an exhaust port for connection toatmosphere, and a port for connection to the element, a valve mechanismin said housing having separate passages connected respectively to saidintake and exhaust ports, and said valve mechanism including meansoperable selectively to connect said element port through said passagesto said intake and exhaust ports, check valve means to control theexhaust port so as to permit fluid medium under super atmosphericpressure to exhaust through said exhaust port, but precluding re-entryof said fluid medium from the atmosphere, and restricted fluid conduitmeans in said valve mechanism and between said element and a source ofsub-atmospheric pressure for permitting deflation of said element undersub-atmospheric pressure upon the super atmospheric pressure beingexhausted from the element through said exhaust port.

DONALD M. LAWRENCE.

REFERENCES CITED 1 The following references are of record in the file ofthis patent:

UNITED- STATES PATENTS Number Name ljate 1,825,443 Chormann et a1. Sept.29, 1931 1,990,866 Gregg Feb. 12, 1935 2,100,154 Ashton Nov. 23, 19372,113,253 Gray Apr. 5, 1938 2,217,299 Taylor Oct. 8, 1940 2,233,934Backhouse Mar. 4, 1941 2,235,138 Billetter Mar. 18, 1941 2,251,430Taylor Aug. 5, 1941 2,331,580 Slawn Oct. 12, 1942 Certificate ofCorrection Patent No. 2,478,492. August 9, 1949.

DONALD M. LAWRENCE It is hereby certified that errors appear in theprinted specification of the above numbered patent requiring correctionas follows:

Column 7, line 32, claim 3, after the Word "boot insert port; line 56,claim 4, for potrs read ports; column 8, line 27, claim 6, forinflatatble read inflatable;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 4th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents.

